#define  _CRT_SECURE_NO_WARNINGS 1
#include<assert.h>
const char* my_strstr(const char* str1, const char* str2)
{
	assert(str1 && str2);
	const char* s1 = NULL;
	const char* s2 = NULL;
	const char* src = str1;
	if (str2=='\0')
	{
		return str1;
	}
	while (*src)
	{
		s1 = src;
		s2 = str2;
		while (*s1 && *s2 && *s1 == *s2)
		{
			s1++;
			s2++;
		}

		if (*s1)
		{
			return NULL;
		}
		if (*s2)
		{
			return src;
		}
		src++;
		
	}
	return NULL;


}